diff --git a/tests/phpunit/tests/functions/underscoreReturn.php b/tests/phpunit/tests/functions/underscoreReturn.php
new file mode 100644
index 0000000000..8c1d2e0962
--- /dev/null
+++ b/tests/phpunit/tests/functions/underscoreReturn.php
@@ -0,0 +1,34 @@
+<?php
+/**
+ * Tests for __return_** set of functions
+ *
+ * @since 5.1.0
+ *
+ * @group functions.php
+ */
+class Tests_Functions_Underscore_Return extends WP_UnitTestCase {
+
+	public function test__return_true() {
+		$this->assertTrue( __return_true() );
+	}
+
+	public function test__return_false() {
+		$this->assertFalse( __return_false() );
+	}
+
+	public function test__return_zero() {
+		$this->assertSame( 0, __return_zero() );
+	}
+
+	public function test__return_empty_array() {
+		$this->assertSame( array(), __return_empty_array() );
+	}
+
+	public function test__return_null() {
+		$this->assertNull( __return_null() );
+	}
+
+	public function test__return_empty_string() {
+		$this->assertSame( '', __return_empty_string() );
+	}
+}